Field of the Invention
This disclosure relates to a sheet feeding apparatus configured to separate and feed sheets and an image forming apparatus including the sheet feeding apparatus.
Description of the Related Art
In many cases, a sheet feeding apparatus provided in an image forming apparatus is configured to separate sheets stacked on a stacking member such as a cassette one by one with a feed roller and the like, and to feed the sheets to a conveyance portion disposed downstream of the feed roller.
Japanese Patent Laid-Open No. 2001-348129 discloses a paper feeder that includes a feed roller configured to feed a paper stacked on a feed tray, a registration roller conveying the sheet to a downstream side of the feed roller, and a control portion to which a sheet size is inputted through an operation panel. The paper feeder causes the feed roller to start rotating, and then, causes the feed roller to stop being driven at a timing at which a trailing edge of a sheet reaches the feed roller, based on the length of the sheet in a feeding direction. In the paper feeder, since the feed roller is continuously driven even after the sheet reaches the registration roller, the registration roller provides assistance to the conveying force of the sheet.
Incidentally, there has been known a sheet feeding apparatus having a configuration for separating sheets using a separation roller. In other words, the sheet feeding apparatus has the configuration that includes a feed roller feeding a sheet in the feeding direction, a separation roller disposed in a pressure contact with the feed roller and to be driven through a torque limiter in a direction against the feeding direction, and a drive unit that drives the feed roller and the separation roller. In this configuration, at least during a period in which the feed roller is driven, drive force is inputted to the separation roller in order to improve sheet separation performance of the separation roller.
Similar to the paper-sheet feeding apparatus disclosed in the above document, in such a sheet feeding apparatus, it is considered that the feed roller continues to be driven even after the sheet reaches the conveyance portion on the downstream side of the feed roller such that the feed roller provides assistance to the convey of the sheet by the conveyance portion. In this manner, it can be expected that double feeding is prevented and the sheet can be stably conveyed.
However, in a case of employing such a configuration, the separation roller repeatedly rotates normally and reversely little by little and vibrates in some cases when the sheet is fed. Then, in the case where a sheet having low stiffness is conveyed, the amplitude of the vibration of the separation roller tends to be increased, compared to a case where a sheet having high stiffness is conveyed. In the case where the separation roller continues vibrating with high amplitude, there is a concern that harsh vibration noise will be produced.